Process of preparing cuprous oxide



4 together redissolves.

the sulphite. I t is my opinion that a complex l Watented pnZl, 1942 fanarts UNITED STATES dAlENT @FFME PRoCEss oF PREPARING @venous oxlDE i William B. Stoddard, Jr., Hamilton, Ohio Application August 22, 1941, Serial No. 407,975 I i (cies-147) d f is allowed to settle and the clear supernatant l Claims. This'invention relates -to a process iof preparing cuprous oxide.

of the original chemicals used may be repeatedly l employed in the preparation of additional quantities of cuprous oxide. I Other objects will become apparent in the course of the following description. r Y y In carrying out the invention according to` the preferred ,procedura a copper salt, advantageously copper sulphate, is allowed to react with a solution of sodium sulphite or other alkali metal sulphite. l The quantities of these two chemicals are so chosen that the precipitate which first forms upon bringing these materials This requires an excess of salt results which appears to have the composition:

Cu2SO3.4Na2SO3 This material is soluble inwater. I prefer to use" the proportions of copper' sulphate and sodium sulphite indicated in the following equation:

More or less sodium sulphite may be used for any given quantity of copper sulphate, but I have 4observed that when using less than 8 moles of liquidl is removed by decantation' or otherwise.

The precipitate is now washed with fresh water f cuprous oxide (CuzOl.

. Moles CuSO4 2 NazSOa 9 HzO 1 NaOH -4 The products of the process comprise:

l Moles CuzO 1 NaiSO4 3` NanSOa 8 H2O 3 After the above mentioned reaction has taken place and the solution has 'become clear and light colored, an alkaline compound of an alkali metal is added, advantageously caustic soda, the

amount of alkali being in accordance with the following equation: y

and it may be boiled for a short time. If desired,

'this washing process may be repeated. Ordinarily this treatment will cause the precipitate to take on a reddish color and the rate of settling is more rapid. l The precipitate .is now removed from the wash water, as by filtration, and may be dried in any desired manner. Depending upon the thoroughness of the washing process, the precipitate will have a copper content of from to 85% or more, and consists largely of It may be more or less hydrated. It has sometimes been noted that the precipitate may carry with it a small amount of some sulphite, but `for most purposes this is not objectionable.

The liquor from which the precipitated cuprous oxide was decanted consists for the most part of a solution of sodium sulphite. In addition it contains a small amount of sodium sulphate. It

that the chemicals used in the process comprise:

Thus it can be seen that whereas the original sodium sulphite solution contained 9 moles NazSOs forxevery 2 moles of .copper sulphate, only one mole of NazSO: has disappeared in the process. It is therefore necessary theoretically discharges into mixing tank I3. The pipe I2 is `provided with a suitable valve I4.

Tank I is also provided with a usual means of calibration whereby the contents may be accurately measured. Tank I3 is equipped with an agitator I5 and a steam coil I6 for heating the contents. Tank I3 is advantageously provided with a cover 39 to prevent or reduce atmospheric oxidation of the materials. Cover 33 is provided with a manhole having a cover,42 for charging solid sodium sulphite into tank I3. Tank II is provided for dissolving the caustic soda. It is connected to tank I3 by means of pipe I8 through a bottom outlet. This pipe is also provided with a valve I9. Tank I3 is connected by a bottom outlet to pipe 20 in which is located valve 2I. Pipe 20 is connected to a pump 22. The discharge side of the pump is connected by pipe 23 to a filter press 24 which may be of the conventionalv type. The filtrate from the filter press may be delivered through pipe 28 to the sewer or through pipe 29 to a storage tank 30 by appropriate manipulation of valves 26 and 2l. Tank 30 has a. bottom outlet to which is connected pipe 3I in which is located valve 32. Tank 30 is also advantageously provided with a close fitting cover 40 to prevent or reduce access of air to the chemicals. Cover 40 is provided with a manhole having a cover 4I for charging solid sodium sulphite into tank 30. Pipe 3| connects storage tank 30 with mixing tank I3. A pipe 33 containing valve 34 is adapted to deliver water to tank I3. Tank I3 is also connected to the pump 22 by means of a pipe 35 containing valve 36. This pipe 35 does not extend clear to the bottom of tank I3 but is advantageously connected to a hose 31 which may be adjusted to different heights and is adapted to draw ofi` liquid from above the level of the precipitate in tank I3.

The following example is given to more particularly illustrate the process as carried out in the above described apparatus. Dissolve 185 pounds of copper sulphate (CuSO4.5HzO) inv 92 gallons of water in tank I0. During this operation the solution is heated to 180 F., after which the solution is allowed to cool somewhat. Eight hundred and sixty pounds of sodium sulphite (NaaSOaJHzO) is charged into tank I3 through manhole 42 and is dissolved in 80 gallons of water in tank I3. The solution is heated to 110 F. using the agitator I5 to hasten the solution of the chemical. Valve I4 in pipe I2 is then opened and a stream of copper sulphate solution at 110 F. is slowly introduced into tank I3, the agitator I5 meantime continuously stirring the liquid. A precipitate first forms but this substantially completely redissolves in the liquid. In order to remove all traces of precipitated material which may be due to impurities present, valve 2| in pipe 20 is opened and the contents of tank I3 are forced through the filter 24 by operation of the pump 22. The filtrate from the filter passes through pipes 25 and 29. During this operation valve 2l is open and valve 28 is closed. By this 75 means the filtrate containing what is believed to be a complex sodium sulphite-copper sulphite solution is transferred to tank 30, the air in tank 30 being displaced through vent 38. Mixing tank I3 vis then rinsed with a small amount of water through pipe 33, which water then passes through the pump 22 and filter 24 through pipes 25 and 29 and is added to the contents of tank 30. Filter 24 is then cleaned. Valve 32 is opened allowing the solution in tank 30 to flow through pipe 3l back into tank I3.

Sixty and one-half pounds of sodium hydroxide is dissolved in 12 gallons of water in tank I l. Valve I9 is then opened allowing the sodium hydroxide to flow through pipe I8 into tank I3. During this operation the agitator I5 is in continuous operation. The agitator is now stopped and the solution allowed to stand over night in order that the precipitate might settle.

'I'he supernatant liquid lying above the precipitate is then carefully drawn off through hose 3l, pipe 35, pump 22, alter' 24 and pumped to storage tank 30. Water is introduced into tank I3 through pipe 33, the agitator put into motion, and steam introduced into the steam coil I6. The mixture is heated to a boiling temperature and boiled for l5 minutes. The agitator is then stopped and the precipitate allowed to settle for about an hour. The supernatant wash water is next pumped through hose 31, pipe 35, and filter 24 and discharged into sewer through pipe 28. The precipitate is again washed with fresh water and the wash water removed as just described. Finally fresh water is introduced into tank I3, the agitator put into motion, valve 2| is opened, and the suspension passed through pipe 20, pump 22, pipe 23, and is filtered in filter 24, the filtrate passing `to the sewer through pipe 28. The precipitate is then removed from the filter and dried in shallow boxes. The dried material consists of a fine reddish powder of relatively pure cuprous oxide, somewhat hydrated. which upon analysis contains about 83% Cu.

The supernatant liquid withdrawn from the precipitate before the washing step and which is held in tank 30, is now'analyzed and ordinarily will require about pounds of sodium sulphite, which is next added thereto through manhole 4I. Valve 32 is opened and the solution allowed to flow into tank I3 and a fresh charge of copper sulphate solution is allowed to flow into tank I3 and the process repeated.

Although the invention has been described with particular reference to the use of copper sulphate, sodium sulphite, and sodium hydroxide, it is not limited to these particular compounds, as other copper salts, sulphites, and alkalies such as sodium carbonate, may be used, as will be apparent to those sk illed in the art. I have also found that alkali metal thiosulphates may be substituted for sulphites in the process.

In place of filtering out the cuprous oxide, a continuous 'centrifuge may be used and the whole process may be carried out substantially continuously.

I claim:

l. Process of preparing cuprous oxide which comprises bringing together in aqueous medium a copper compound and a compound of the class comprising alkali metal `sulphite and alkali metal thiosulphate, thereafter adding an alkaline compsund of an alkali metal, and separating the resulting precipitate from the liquor.

2. Process of preparing cuprous oxide which comprises mixing in water solution a cupric salt a solution of a copper compound with'an excessl v 2,280,168 with sodium sulphite, to the' resulting mixture l adding sodium hydroxide, and separating precipitate containing cuprous oxide. i

3. Process of preparing cuprous oxide which comprises reacting in aqueous medium a soluble sodium sulphite, thereafter adding sodiuml hy droxide in the proportion of about 4'moles sodium hydroxide, and filtering oil the precipitate comprising cuprous oxide.

5. Process of preparing vcuprous oxide which comprises adding a solution of an alkali sulphite to a solution of a copper salt with agitation until the precipitate which forms redissolves, and

alkali metal hydroxide to precipitatev cuprous oxide.

-6. In a cyclic process for the preparation of cuprous oxide the steps which comprise 'mixing of a solution of a compound of the class comprising alkali metal sulphite and alkali metal thiosulphate, adding an alkaline compound ofalkali metaly to precipitate cuprous oxide, separating the cuprous oxide from the, liquor and using said liquor in .the treatmentfof a fresh` supply of copper compound. v

7. In a cyclic process for the preparationof a water solution of a copper compound to a water solution of an alkali metal sulphite in such proportions that the precipitate 'which forms is substantially completely redissolved,

addingV alkali metal hydroxide to the resulting solution to precipitate cuprous oxide, separating cuprous oxide the steps which comprise adding the cuprous oxide from the liquor, and using said liquor in the treatment of a fresh batch of copper compound.

8. In a.cyc1ic process for the preparation of cuprous oxide the steps which comprise adding a solution of copper sulphate to a'n excess of a solution of sodium sulphite, filtering oil any `insoluble material, adding a solution of sodium hydroxide to precipitate cuprous oxide, filtering oif the cuprous oxide and re-sing the filtrate containing sodium sulphite and sodium sulphate for further treatment with a freshsupply of copper sulphate solution. l

9. In a cyclic process the-steps which comprise mixing together under conditions of agita- `tion a solution of copper sulphate and sodium sulphite to form a water, soluble complex'comprising cuprous sulphite and sodium sulphite, filtering ofi any insoluble matter, adding sodium hydroxide to precipitate cuprous oxide, allowing the precipitate to settle, remoi'iing the supernatant liquid containing sodium sulphite, washing the precipitate with water, boiling the precipitate with water, separating the precipitate from the wash water and drying the precipitate,

replenishing the aforesaid supernatant liquid with sodium sulphite to bring the sodium sulphite content up to about the content of the original sodium sulphite solution, adding` a fresh supply of copper sulphate to said replenished. liquor, and repeating the process.

l0. AV cyclic process for the preparation of cuprous oxide which comprises mixing solutions of a cupric salt and alkali metal sulphite in the proportions of from three to ilve moles of sulphite for each mole of cupric salt, adding alkali metal hydroxide to precipitate cuprous hydroxide, Vseparating the precipitate from the liquor, replenishing' the' liquor with alkali metal sulphite to about its original content of alkali metal sulphite, and repeating the process with a fresh charge of cupric salt.

- B. s'roDDARD, Ja. 

